Project Summary (Abstract) This proposal explores the neural and psychological mechanisms that underlie older adult decision-making, particularly decisions about whether or not to engage in cognitively effortful activities. Basic research in the cognitive neuroscience of aging has suggested that older adults show declines in the ability to control thoughts and actions based on internal goals, and that this may stem from age-related changes in the functioning of the prefrontal cortex and mid-brain dopamine system. Yet older adults also seem to experience clear shifts in motivational prioritization, although currently the relationship between motivation, cognition function, and decision-making is poorly understood. The current proposal provides a novel perspective on this issue, by focusing on interactions between motivation and cognitive control through the conceptual lens of neuroeconomic decision-making. Specifically, we build upon a recent theoretical framework, value-based cognitive control (VBCC), which postulates that motivational value serves to counteract the subjective and computational costs of engaging in cognitive control. A key implication of the VBCC framework is that age- related motivational reprioritization may shift cost-benefit computations, leading towards increased subjective costs associated with engagement in cognitively effortful activities. The project directly tests this hypothesis, utilizing an innovative neuroeconomic decision-making paradigm known as the COG-ED (Cognitive Effort Discounting), which provides the means to quantitatively estimate the subjective cost of cognitive effort. We utilize the COG-ED to examine the neural mechanisms associated with potentially increased cognitive effort costs in older adults, using state-of-the-art neuroimaging methods. Specifically, we employ simultaneous PET/fMRI scanning to both monitor effort-related activity in brain regions associated with encoding of subjective motivational value, while at the same time directly assessing dopamine function in these regions. We further test the domain-generality of our theoretical framework, utilizing the COG-ED and a within-subjects neuroimaging design to test for increased cognitive effort costs among older adults in both working memory and speech comprehension. We rigorously explore the ecological validity of the VBCC framework, by repeatedly sampling older adult daily-life experiences and motivations towards cognitively effortful activities with a naturalistic, ecological momentary assessment (EMA) approach. This project component enables a strong test of cross-level bridging hypotheses, such as whether age-related declines in brain valuation mechanisms contribute to increased cognitive effort costs and reduced engagement in daily-life effortful activities among older adults. The findings of this project have high